Experimental Study Of Flow And Heat Transfer Characteristics At SCWR Typical Conditions

Under the typical conditions of SCWR(Super-critical Water-Cooled Reactor), which is the only water cooled reactor of Generation IV reactors, the coolant flow and heat transfer in fuel assembly at supercritical pressure are obviously different from that at subcritical pressure. Heat transfer deterioration caused by heat transfer coefficient decreasing would occur under low mass flow rate and high heat flux conditions. The traditional Dittus-Boelter correlation is not applicable in the typical condition of SCWR, which brings enormous challenge for the SCWR fuel assembly design. Based on the SCWR-M(SCWR With Mixed Spectrum) fuel assembly proposed by Shanghai Jiao Tong University, this dissertation presents supercritical water thermal-hydraulic experiment in tube under the typical condition of SCWR-M. The experiment and mechanism analysis obtains further understanding of heat transfer enhancement and heat transfer deterioration, develops more effective and universal correlation, and establishes foundation of SCWR-M fuel assembly design.The main contents of this dissertation include:1. SWAMUP facility was set up and thermal-hydraulic experiments were conducted under typical condition of SCWR-M: Pressure range P= 23~26MPa, Inlet mass flow rate range G=450~1500 kg/(m~2.s) and Heat flux range q=300~2000 kW/m~2 in a tube with hydraulic diameter of 7.6 mm. Upward and downward experiments are both performed to analyze the flow and heat transfer behaviors influenced by thermal-hydraulic parameters and flow direction.2. A semi-empirical heat transfer correlation is developed and evaluated based on the heat transfer experimental data, which can predict heat transfer enhancement and heat transfer deterioration phenomenon, rather than normal heat transfer of supercritical water.3. A pressure drop correlation is obtained based on the pressure drop experimental data.3. Using CFD(Computational Flud Dynamics) method, 8 low-Reynolds turbulent models are validated to analyze the mechanisms of heat transfer deterioration: JL, HP, CH, AKN, LS, MK, NK and ZH-AFM models are simulated to compare to 4 experimental conditions by the temperature field, flow field and turbulence information. The optimal ZH-AFM model is selected according to the experimental data comparison, which can explain the mechanisms of buoyancy-oriented and acceleration-oriented heat transfer deterioration in phenomena.This dissertation reveals the mechanisms of heat transfer deterioration under typical condition of supercritical water, obtains a semi-empirical heat transfer correlation and pressure drop correlation, and shows significant meaning to the SCWR fuel assembly thermal-hydraulic design.